I've stumbled upon a Yamaha CS15 for £500. The seller says the synth is in excellent shape and I have no reason to doubt that.Let's assume the best for the sake of this post! Meanwhile, a friend has offered me his Mono/Poly for the same price. I know that's an amazing price for the Korg, but the synth does have some issues. Mainly, one of the oscillators won't tune up. My friend took it in for repair but couldn't get anywhere. His incredible price to me on the Korg is conditional - I'd take the synth in for repair in Berlin, where there are far more people able to sort it out than in his small Scottish town. And if I sold the synth, I'd give my mate first right of refusal. All sounds good.

I've not played a CS15 before - I've spent a bit of time with the CS5 and quite liked it. I remember the Mono/Poly mostly from the music store, back in the day. I never took to it, but that doesn't mean I wouldn't dig it these days.

Both are much-loved synths, and I'm curious which you folks would pick of the two at that price.

I think the CS15 would be a better fit with your other synths. Plus you already like the CS sound. A great deal for a synth that needs service almost always turns out to not be such a great deal in the end!

Even though I'm a huge fan of the Mono/Poly, they are more prone to age-related issues than the CS15 (my Mono/Poly is starting to get a bit sick, whereas my CS15 is working perfectly).

Also, as an aside, I recently bought a DSI Pro-2 which I think is pretty much like a suped-up 21st century version of the Mono/Poly, albeit minus the SSM filter but with much more sonic potential. I am tending to use the Pro-2 more than my Mono/Poly for 4-Osc sounds & weird 'paraphonic' things, so it might make an good alternative to the Mono/Poly if you wanted that type of synth architecture.

Thanks for the input, guys. Yeah, I think the CS15 would likely be more my thing, and concerns for upkeep on the Korg already weigh on me. Some of it's vibe, too. I'm often as much affected by the look and feel of certain synths as I am by the sound. I had a PolySix for years and loved it, but never took to the Mono/Poly, despite similar layout. But really, the Yamaha calls to me in a way the Korg doesn't.

I say all this knowing that all my coins need to point their way towards a Prophet 6 anyway. Don't I already have enough mono synths? (Don't answer that!)

Before the thread moves too far into alternate suggestions, I just wanted to point out that although the CS monos have better service records than the Korgs, once something fails it is going to be very expensive to find replacement parts, if you can find them at all. My CS-15 has two noisy VCA's that I'm told means they have both switched to a "failure mode", so its days are numbered. The small multi-position switches get flaky on nearly all of them as well, and replacements are rare.

The CS does not have any of the microprocessor functions of the Mono/Poly, such as the arpeggiator and polyphonic keyboard, the CS does not have hard sync or crossmod, the Mono Poly of course has two more oscillators and the CS has a pair of multi-mode 2 pole filters, versus the Korg's 4 pole lowpass filter with self-oscillation. The CS filter tracking of keyboard is permanently fixed at about 90%, where the Korg's is adjustable. The Korg's envelopes and CS5's envelopes are faster than the CS-15's, but the CS instead has an envelope mode to greatly -extend- envelope times. The CS does not have a modwheel, but does have a cool slider to tweak both filters' cutoff simultaneously. The CS filters and amps can be controlled by either envelope. CS LFO has random waveform, where Mono-poly's has reverse sawtooth and square. The Korg's keyboard has a multi-trigger mode for the gate and a CV input for VCF control.

Alot of people say the CS sounds more bland, more like VA, but it does have some advantages in character if you're willing to explore. Alot of CS-15 owners seem to praise the pulsewidth modulation sound, but remember that the CS rectangle waveform sounds more dull in tone than its sawtooth waveform. Also the CS does not have envelope control of pulsewidth, while the Korg does. Having two filters in parallel means more tonal variety, which some feel is the real beauty of the CS-15. This will take time however, as the CS-15 doesn't really have alot of easy to find "sweet spots".

I did the serial channel mod on my CS-15, which can reroute VCF2 output to the input of VCF1, making 4 pole filtering possible. You can still control the resonance and envelope/modulation of each filter while they are chained to get some fatter sounds, plus VCO1 can also be mixed back in to add some extra depth.There apparently is a fairly basic mod for adding oscillator sync, and it would also be easy to add CV inputs for each VCF cutoff control. I've not done these, mostly due to a lack of interest. Wish there was a way to set filter tracking to zero. The CS has a generally "sweet" midrange tone that is elsewhere in the spectrum kind of flat. Bass is good but other monosynths do it much better. It can be pushed into saturation by sending the headphone output back to the Audio input when VCF1 is in Highpass mode, which also allows for a somewhat unwieldy self-oscillation.It's fun to tweak and as I said, has some unique offerings in character if you spend the time.Here is a recent quick demo I did of only rectangle waveform sounds on my serial-channel modded CS-15:

I am no longer in pursuit of vintage synths. The generally absurd inflation from demand versus practical use and maintenance costs is no longer viable. The internet has suffocated and vanquished yet another wonderful hobby. Too bad.--Solderman no more.

Well that is an excellent review of the CS. You could not do better. I would like to add a clarification if I may. In general I think envelope times are not a good metric for punchiness, or any sonic qualities at all really. It's the shape that really determines the sound. But we tend to use times because that's a simple number, whereas shape or curves are more challenging to understand. The CS10 and 15 have an initial level control on the attack time, which gives you a range of plucking type effects, and is excellent for punchy bass sounds. I sold my set up of 2 CS5s plus CS10 and replaced them with the Novation KS rack. It does the sweet PWM sound, has random LFO, and the filter can do the same sweet thing that the CS does, but it has more range, probably because of variable tracking and no limit on the resonance.

But I've never used a CS15, except for the time I missed out on one for €70 (it's a funny story). I really hope Automatic Gainsay will be along soon to vilify me for my assumptions about the CS15, and his disgust at my love of a run of the mill VA

Yamaha had some amazing engineers back in the 70's. I've owned a CS-15 that was in perfect cosmetic and physical shape. I still have a CS-5 that has never been overhauled but still runs like clockwork when I turn it on a few times a year.

Bit startled to check back in on the thread only to find such ravery for the CS15! In regards my going instead for polysynth, well, the P6 is on my list no matter what. I have a Juno 6 now, and back home I have a Polysix and a P5 I can use when I need. I know many of you understand that adding another monosynth is simply like adding another year to one's age. It just happens whether one wishes it or not!

On one hand I do go with gut instinct more often than not. I've never been that taken with the Mono/Poly, for whatever reason. On the other hand, I'm always more than willing to give something another chance. I was very pro-PolySix, very anti-Juno wayyyy back, as though it matter to choose sides. Now having a Juno 6, I see what the fuss is about. I'm sure I'd probably love the Mono/Poly, but given the various problems the one offered to me already has and the problems it might be likely to have, I'm not very keen on it now. The CS15 still pulls me. Of the CS monos, I've only played a CS5, but took to it immediately. Maybe cos it was the only synth in the room, but it had a vibe that got me right away.

For as synth'd out as I've been for so many years (Got my first Pro One when I was 13, and I ain't 13 anymore!), I'm pretty naive. I can program sounds no sweat... but talk to me about filter chips and I tune out. h**l, even "snappy envelopes" is ALMOST too tech for me. Maybe I treat each synth as an organic entity unto itself and take them for what they do, not so much what they don't/can't do. That said, with a Pro One for osc sync sounds (and in a way, that's THE sync sound, in a way), I'm sorted there. I like the idea of a nice slider-y synth, sure why not!

Thanks also for the mod tips. Again, I'm not tech in a circuit-bendy way, but I'm happy to plug things in where they only sorta belong. I say all this, yet I haven't actually bought the CS15. Pretty sure I'm convinced that if I can, I ought, though. AND the P6 of course.

Cheers, guys...

Last edited by Grumblepig on Wed Jan 06, 2016 2:47 pm, edited 1 time in total.

based on what you said and what you have, id go for the cs15. if you liked the cs5, the dual oscillators and filters of the cs15 will probably make you really happy. the monopoly can generally make more extreme / less polite sounds than the cs15 can, but most of the synths youve already got can cover that territory well. good luck!mini